Films having a combination of high impact strength and high shrink

Abstract

Heat shrinkable films having at least one layer comprising a blend of a first ethylene/alpha-olefin copolymer having a M w /M n of from about 1 to 3.0 and a second ethylene/alpha-olefin copolymer having an Mw/Mn greater than 3.0. The first ethylene/alpha-olefin copolymer has a density of from about 0.91 g/cc to about 0.925 g/cc, a first melting point of from about 85° C. to about 110° C., and a second melting point of from about 111° C. to about 125° C. The second ethylene/alpha-olefin copolymer has a density of from about 0.90 to about 0.91 g/cc. The first ethylene/alpha-olefin copolymer makes up from about 5 to about 40 weight percent of the blend. The second ethylene/alpha-olefin makes up from about 60 to about 95 weight percent of the blend. The blend makes up from about 40 to 100 weight percent of the total weight of the film. The film has a total free shrink at 85° C. of at least 60 percent and a peak load impact strength of at least 135 Newtons per mil. The film can be monolayer or multilayer and multilayer films can comprise a second layer comprising a thermoplastic polymer.

1 . A multilayer film comprising a first layer comprising a blend of: 
 (1) a first ethylene/alpha-olefin copolymer having a M w /M n  of from about 1 to 3.0 and a density of from about 0.91 g/cc to about 0.925 g/cc, the first ethylene/alpha-olefin copolymer having a first melting point of from about 85° C. to about 110° C. and a second melting point of from about 111° C. to about 125° C.; and    (2) a second ethylene/alpha-olefin copolymer having an Mw/Mn greater than 3.0 and a density of from about 0.90 to about 0.91 g/cc;    wherein the first ethylene/alpha-olefin copolymer comprises from about 5 to about 40 weight percent of the blend, and the second ethylene/alpha-olefin comprises from about 60 to about 95 weight percent of the blend, and wherein the total amount of the blend in the first layer and in any other layers of the film comprises from about 40 to about 99 weight percent of the total weight of the multilayer film, with the multilayer film having a total free shrink at 85° C. of at least 60 percent and a peak load impact strength of at least 135 Newtons per mil, with the multilayer film further comprising a second layer comprising a thermoplastic polymer.    
   
   
       2 . The multilayer film according to  claim 1 , wherein: 
 (A) the first ethylene/alpha-olefin copolymer has a M w /M n  of from about 2 to about 2.5 and a density of from about 0.910 g/cc to about 0.915 g/cc, with the first melting point of from about 92° C. to about 107° C., and a second melting point of from about 115° C. to about 120° C.,    (B) the second ethylene/alpha-olefin copolymer has a density of from about 0.900 to about 0.906 g/cc; and    wherein the first ethylene/alpha-olefin copolymer makes up from about 7 to 35 weight percent of the blend, and the second ethylene/alpha-olefin makes up from about 70 to about 90 weight percent of the blend, and wherein the blend makes up from about 40 to about 80 weight percent of the total weight of the multilayer film, with the multilayer film having a total free shrink at 85° C. of from about 80 to about 100 percent and a peak load impact strength of from 135 to about 155 Newtons per mil.    
   
   
       3 . The multilayer film according to  claim 1 , wherein: 
 (A) the first ethylene/alpha-olefin copolymer has a M w /M n  of from about 2.2 to about 2.4 and a density of from about 0.911 g/cc to about 0.913 g/cc, the first melting point being within a range of from about 100° C. to about 103° C., the second melting point being within a range of from about 116° C. to about 118° C.; and    (B) the second ethylene/alpha-olefin copolymer has a density of from about 0.902 to about 0.904 g/cc; and    wherein the first ethylene/alpha-olefin copolymer makes up from about 15 to about 25 weight percent of the blend, and the second ethylene/alpha-olefin makes up from about 75 to about 85 weight percent of the blend, and wherein the blend makes up from about 55 to about 65 weight percent of the total weight of the multilayer film, with the multilayer film having a total free shrink at 85° C. of from about 80 to about 90 percent and a peak load impact strength of from 140 to about 155 Newtons per mil.    
   
   
       4 . The multilayer film according to  claim 1 , wherein the film has an energy to break of at least 2.3 Joules/mil.  
   
   
       5 . The multilayer film according to  claim 1 , wherein the film has an energy to break of from about 2.5 to about 2.9 Joules/mil.  
   
   
       6 . The multilayer film according to  claim 1 , wherein the film has an energy to break of from about 2.69 to about 2.84 Joules/mil.  
   
   
       7 . The multilayer film according to  claim 1 , wherein the first ethylene/alpha-olefin copolymer has been polymerized using a metallocene catalyst on a solid support.  
   
   
       8 . The multilayer film according to  claim 1 , wherein the first ethylene/alpha-olefin copolymer comprises a copolymer of ethylene and at least one member selected from the group consisting of butene, hexene, and octene.  
   
   
       9 . The multilayer film according to  claim 1 , wherein the second ethylene/alpha-olefin copolymer comprises a copolymer of ethylene and at least one member selected from the group consisting of butene, hexene, and octene.  
   
   
       10 . The multilayer film according to  claim 1 , wherein the first ethylene/alpha-olefin copolymer has a melt index of from about 0.1 to about 5 g/10 min.  
   
   
       11 . The multilayer film according to  claim 1 , wherein the second ethylene/alpha-olefin copolymer has a melt index of from about 0.1 to about 2 g/10 min.  
   
   
       12 . The multilayer film according to  claim 1 , wherein the film has a total thickness of from about 0.2 mil to about 10 mils.  
   
   
       13 . The multilayer film according to  claim 1 , wherein the film has a total thickness of from about 1.5 mils to about 3.5 mils.  
   
   
       14 . The multilayer film according to  claim 1 , wherein the film has a total thickness of from about 2 mils to about 3 mils.  
   
   
       15 . The multilayer film according to  claim 1 , wherein the second layer serves as an O 2 -barrier layer, the second layer comprising at least one member selected from the group consisting of ethylene/vinyl alcohol copolymer, polyvinyl chloride, polyvinylidene chloride, polyamide, polyester, polyacrylonitrile.  
   
   
       16 . The multilayer film according to  claim 15 , further comprising a third layer which serves as a seal layer, the third layer being an outer layer, with the first layer being between the third layer and the second layer.  
   
   
       17 . The multilayer film according to  claim 16 , further comprising a fourth layer which is a second outer layer, with the second layer being between the first layer and the fourth layer.  
   
   
       18 . The multilayer film according to  claim 17 , further comprising a fifth layer which is between the fourth layer and the second layer, the fifth layer containing a polymeric composition in accordance with the blend of the first layer.  
   
   
       19 . The multilayer film according to  claim 18 , further comprising: 
 (A) a sixth layer between the second layer and the first layer, the sixth layer serving as a first tie layer; and    (B) a seventh layer between the second layer and the fifth layer, the seventh layer serving as a second tie layer.    
   
   
       20 . A bag made from a multilayer film sealed to itself, the multilayer film having a first layer and a second layer, the first layer containing a blend of: 
 (A) a first ethylene/alpha-olefin copolymer having a M w /M n  of from about 1 to 3.0 and a density of from about 0.91 g/cc to about 0.925 g/cc, the first ethylene/alpha-olefin copolymer having a first melting point of from about 85° C. to about 110° C. and a second melting point of from about 111° C. to about 125° C.; and    (B) a second ethylene/alpha-olefin copolymer having an Mw/Mn greater than 3.0 and a density of from about 0.90 to about 0.91 g/cc; and    wherein the first ethylene/alpha-olefin copolymer makes up from about 5 to about 40 weight percent of the blend, and the second ethylene/alpha-olefin makes up from about 60 to about 95 weight percent of the blend, and wherein the blend makes up from about 40 to 80 weight percent of the total weight of the multilayer film, with the multilayer film having a total free shrink at 85° C. of at least 60 percent and a peak load impact strength of at least 135 Newtons per mil, with the second layer comprising a thermoplastic polymer.